This invention relates to a thread tensioning device for use with textile machinery. Heretofore, tensioning devices have been provided which utilize a chamber having a spherical ball seated on an eyelet through which the thread passes whereby the weight of the ball tensions the thread such as shown in U.S. Pat. No. 3,892,371 and 4,017,038. The tension is varied either by using balls of different weight or by providing a plurality of balls in series which makes accurate tension control troublesome.
Other type devices have been proposed to provide more accurate tension control such as the magnetic arrangements for tensioning thread shown in U.S. Pat. No. 3,897,916 wherein magnetic force is used to brake and control the rotation of a wheel about which thread is wound for tensioning. However, such devices tend to become unduly complicated and expensive for the large numbers required in the market.
It has also been known to provide thread tensioning devices of the type in which thread is drawn over a friction member as it passes toward the textile machine with the tension of the thread being varied by changing the extent to which the thread contacts the surface of the tensioning member such as shown in U.S. Pat. No. 1,596,095. However, the problem occurs in devices of this type that during machine stoppage, the thread in contact with the friction member loses contact and becomes loose about the friction member whereby upon start-up of the machine, the thread is jerked against the friction member often resulting in thread breakage and damage.
Accordingly, an important object of the present invention is to provide a thread tensioning device which tensions thread simply and accurately and brake therefor.
Yet another important object of the present invention is to provide a thread tensioning and brake device which holds the thread tensioned during machine stoppage to avoid thread breakage.
Still another important object of the present invention is to provide a thread tensioning device which is maintained relatively free of dirt and lint and may be easily cleaned.